chore: [WIP] refactor pick server scene with diffable data source

Mastodon.xcodeproj/project.pbxproj

@@ -96,6 +96,12 @@
 		DB0AC6FC25CD02E600D75117 /* APIService+Instance.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB0AC6FB25CD02E600D75117 /* APIService+Instance.swift */; };
 		DB118A8225E4B6E600FAB162 /* Preview Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = DB118A8125E4B6E600FAB162 /* Preview Assets.xcassets */; };
 		DB118A8C25E4BFB500FAB162 /* HighlightDimmableButton.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB118A8B25E4BFB500FAB162 /* HighlightDimmableButton.swift */; };
+		DB1FD43625F26899004CFCFC /* MastodonPickServerViewModel+LoadIndexedServerState.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB1FD43525F26899004CFCFC /* MastodonPickServerViewModel+LoadIndexedServerState.swift */; };
+		DB1FD44425F26CCC004CFCFC /* PickServerSection.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB1FD44325F26CCC004CFCFC /* PickServerSection.swift */; };
+		DB1FD44A25F26CD7004CFCFC /* PickServerItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB1FD44925F26CD7004CFCFC /* PickServerItem.swift */; };
+		DB1FD45025F26FA1004CFCFC /* MastodonPickServerViewModel+Diffable.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB1FD44F25F26FA1004CFCFC /* MastodonPickServerViewModel+Diffable.swift */; };
+		DB1FD45A25F27898004CFCFC /* CategoryPickerItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB1FD45925F27898004CFCFC /* CategoryPickerItem.swift */; };
+		DB1FD46025F278AF004CFCFC /* CategoryPickerSection.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB1FD45F25F278AF004CFCFC /* CategoryPickerSection.swift */; };
 		DB2B3ABC25E37E15007045F9 /* InfoPlist.strings in Resources */ = {isa = PBXBuildFile; fileRef = DB2B3ABE25E37E15007045F9 /* InfoPlist.strings */; };
 		DB2B3AE925E38850007045F9 /* UIViewPreview.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB2B3AE825E38850007045F9 /* UIViewPreview.swift */; };
 		DB2F073525E8ECF000957B2D /* AuthenticationViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = DB2F073325E8ECF000957B2D /* AuthenticationViewModel.swift */; };
@@ -310,6 +316,12 @@
 		DB0AC6FB25CD02E600D75117 /* APIService+Instance.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "APIService+Instance.swift"; sourceTree = "<group>"; };
 		DB118A8125E4B6E600FAB162 /* Preview Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = "Preview Assets.xcassets"; sourceTree = "<group>"; };
 		DB118A8B25E4BFB500FAB162 /* HighlightDimmableButton.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HighlightDimmableButton.swift; sourceTree = "<group>"; };
+		DB1FD43525F26899004CFCFC /* MastodonPickServerViewModel+LoadIndexedServerState.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "MastodonPickServerViewModel+LoadIndexedServerState.swift"; sourceTree = "<group>"; };
+		DB1FD44325F26CCC004CFCFC /* PickServerSection.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PickServerSection.swift; sourceTree = "<group>"; };
+		DB1FD44925F26CD7004CFCFC /* PickServerItem.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = PickServerItem.swift; path = Mastodon/Diffiable/Section/PickServerItem.swift; sourceTree = SOURCE_ROOT; };
+		DB1FD44F25F26FA1004CFCFC /* MastodonPickServerViewModel+Diffable.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "MastodonPickServerViewModel+Diffable.swift"; sourceTree = "<group>"; };
+		DB1FD45925F27898004CFCFC /* CategoryPickerItem.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CategoryPickerItem.swift; sourceTree = "<group>"; };
+		DB1FD45F25F278AF004CFCFC /* CategoryPickerSection.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CategoryPickerSection.swift; sourceTree = "<group>"; };
 		DB2B3ABD25E37E15007045F9 /* en */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = en; path = en.lproj/InfoPlist.strings; sourceTree = "<group>"; };
 		DB2B3AE825E38850007045F9 /* UIViewPreview.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = UIViewPreview.swift; sourceTree = "<group>"; };
 		DB2F073325E8ECF000957B2D /* AuthenticationViewModel.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AuthenticationViewModel.swift; sourceTree = "<group>"; };
@@ -456,11 +468,13 @@
 		0FAA102525E1125D0017CCDE /* PickServer */ = {
 			isa = PBXGroup;
 			children = (
-				0FB3D31825E525DE00AAD544 /* CollectionViewCell */,
 				0FB3D30D25E525C000AAD544 /* View */,
+				0FB3D31825E525DE00AAD544 /* CollectionViewCell */,
 				0FB3D2FC25E4CB4B00AAD544 /* TableViewCell */,
 				0FAA102625E1126A0017CCDE /* MastodonPickServerViewController.swift */,
 				0FB3D2F625E4C24D00AAD544 /* MastodonPickServerViewModel.swift */,
+				DB1FD44F25F26FA1004CFCFC /* MastodonPickServerViewModel+Diffable.swift */,
+				DB1FD43525F26899004CFCFC /* MastodonPickServerViewModel+LoadIndexedServerState.swift */,
 			);
 			path = PickServer;
 			sourceTree = "<group>";
@@ -642,6 +656,8 @@
 			isa = PBXGroup;
 			children = (
 				2D76319E25C1521200929FB9 /* StatusSection.swift */,
+				DB1FD44325F26CCC004CFCFC /* PickServerSection.swift */,
+				DB1FD45F25F278AF004CFCFC /* CategoryPickerSection.swift */,
 			);
 			path = Section;
 			sourceTree = "<group>";
@@ -683,6 +699,8 @@
 			isa = PBXGroup;
 			children = (
 				2D7631B225C159F700929FB9 /* Item.swift */,
+				DB1FD44925F26CD7004CFCFC /* PickServerItem.swift */,
+				DB1FD45925F27898004CFCFC /* CategoryPickerItem.swift */,
 			);
 			path = Item;
 			sourceTree = "<group>";
@@ -1464,8 +1482,10 @@
 				2D38F1F725CD47AC00561493 /* HomeTimelineViewModel+LoadOldestState.swift in Sources */,
 				0FB3D33225E5F50E00AAD544 /* PickServerSearchCell.swift in Sources */,
 				2D5A3D3825CF8D9F002347D6 /* ScrollViewContainer.swift in Sources */,
+				DB1FD45A25F27898004CFCFC /* CategoryPickerItem.swift in Sources */,
 				0FAA101225E105390017CCDE /* PrimaryActionButton.swift in Sources */,
 				DB8AF53025C13561002E6C99 /* AppContext.swift in Sources */,
+				DB1FD44A25F26CD7004CFCFC /* PickServerItem.swift in Sources */,
 				DB72602725E36A6F00235243 /* MastodonServerRulesViewModel.swift in Sources */,
 				2D364F7225E66D7500204FDC /* MastodonResendEmailViewController.swift in Sources */,
 				2D38F1F125CD477D00561493 /* HomeTimelineViewModel+LoadMiddleState.swift in Sources */,
@@ -1511,12 +1531,14 @@
 				2DF75BA125D0E29D00694EC8 /* StatusProvider+TimelinePostTableViewCellDelegate.swift in Sources */,
 				2D42FF7E25C82218004A627A /* ActionToolBarContainer.swift in Sources */,
 				DB0140A125C40C0600F9F3CF /* MastodonPinBasedAuthenticationViewController.swift in Sources */,
+				DB1FD43625F26899004CFCFC /* MastodonPickServerViewModel+LoadIndexedServerState.swift in Sources */,
 				2D939AE825EE1CF80076FA61 /* MastodonRegisterViewController+Avatar.swift in Sources */,
 				2D5981A125E4A593000FB903 /* MastodonConfirmEmailViewModel.swift in Sources */,
 				DB8AF55025C13703002E6C99 /* MainTabBarController.swift in Sources */,
 				DB9D6BE925E4F5340051B173 /* SearchViewController.swift in Sources */,
 				2D38F1C625CD37F400561493 /* ContentOffsetAdjustableTimelineViewControllerDelegate.swift in Sources */,
 				DB6C8C0F25F0A6AE00AAA452 /* Mastodon+Entity+Error.swift in Sources */,
+				DB1FD44425F26CCC004CFCFC /* PickServerSection.swift in Sources */,
 				0FB3D30F25E525CD00AAD544 /* PickServerCategoryView.swift in Sources */,
 				DB2F073525E8ECF000957B2D /* AuthenticationViewModel.swift in Sources */,
 				DB68A04A25E9027700CFDF14 /* DarkContentStatusBarStyleNavigationController.swift in Sources */,
@@ -1533,10 +1555,12 @@
 				DB118A8C25E4BFB500FAB162 /* HighlightDimmableButton.swift in Sources */,
 				DB084B5725CBC56C00F898ED /* Toot.swift in Sources */,
 				DB0140A825C40C1500F9F3CF /* MastodonPinBasedAuthenticationViewModelNavigationDelegateShim.swift in Sources */,
+				DB1FD45025F26FA1004CFCFC /* MastodonPickServerViewModel+Diffable.swift in Sources */,
 				DB2B3AE925E38850007045F9 /* UIViewPreview.swift in Sources */,
 				DB427DD625BAA00100D1B89D /* AppDelegate.swift in Sources */,
 				DB9D6C0E25E4F9780051B173 /* MosaicImageViewContainer.swift in Sources */,
 				DB98338725C945ED00AD9700 /* Strings.swift in Sources */,
+				DB1FD46025F278AF004CFCFC /* CategoryPickerSection.swift in Sources */,
 				DB45FAB625CA5485005A8AC7 /* UIAlertController.swift in Sources */,
 				DBE0821525CD382600FD6BBD /* MastodonRegisterViewController.swift in Sources */,
 				2D5A3D0325CF8742002347D6 /* ControlContainableScrollViews.swift in Sources */,

Mastodon.xcodeproj/xcuserdata/mainasuk.xcuserdatad/xcschemes/xcschememanagement.plist

@@ -22,7 +22,7 @@
 		<key>Mastodon.xcscheme_^#shared#^_</key>
 		<dict>
 			<key>orderHint</key>
-			<integer>12</integer>
+			<integer>8</integer>
 		</dict>
 	</dict>
 	<key>SuppressBuildableAutocreation</key>

Mastodon/Diffiable/Item/CategoryPickerItem.swift

@@ -0,0 +1,76 @@
+//
+//  CategoryPickerItem.swift
+//  Mastodon
+//
+//  Created by Cirno MainasuK on 2021/3/5.
+//
+
+import Foundation
+import MastodonSDK
+
+enum CategoryPickerItem {
+    case all
+    case category(category: Mastodon.Entity.Category)
+}
+
+extension CategoryPickerItem {
+    var title: String {
+        switch self {
+        case .all:
+            return L10n.Scene.ServerPicker.Button.Category.all
+        case .category(let category):
+            switch category.category {
+            case .academia:
+                return "📚"
+            case .activism:
+                return "✊"
+            case .food:
+                return "🍕"
+            case .furry:
+                return "🦁"
+            case .games:
+                return "🕹"
+            case .general:
+                return "💬"
+            case .journalism:
+                return "📰"
+            case .lgbt:
+                return "🏳️‍🌈"
+            case .regional:
+                return "📍"
+            case .art:
+                return "🎨"
+            case .music:
+                return "🎼"
+            case .tech:
+                return "📱"
+            case ._other:
+                return "❓"
+            }
+        }
+    }
+}
+
+extension CategoryPickerItem: Equatable {
+    static func == (lhs: CategoryPickerItem, rhs: CategoryPickerItem) -> Bool {
+        switch (lhs, rhs) {
+        case (.all, .all):
+            return true
+        case (.category(let categoryLeft), .category(let categoryRight)):
+            return categoryLeft.category.rawValue == categoryRight.category.rawValue
+        default:
+            return false
+        }
+    }
+}
+
+extension CategoryPickerItem: Hashable {
+    func hash(into hasher: inout Hasher) {
+        switch self {
+        case .all:
+            hasher.combine(String(describing: CategoryPickerItem.all.self))
+        case .category(let category):
+            hasher.combine(category.category.rawValue)
+        }
+    }
+}

Mastodon/Diffiable/Item/Item.swift

@@ -30,7 +30,7 @@ protocol StatusContentWarningAttribute {
 }
 
 extension Item {
-    class StatusTimelineAttribute: Hashable, StatusContentWarningAttribute {
+    class StatusTimelineAttribute: Equatable, Hashable, StatusContentWarningAttribute {
         var isStatusTextSensitive: Bool
         var isStatusSensitive: Bool
 
@@ -51,7 +51,6 @@ extension Item {
             hasher.combine(isStatusTextSensitive)
             hasher.combine(isStatusSensitive)
         }
-
     }
 }
 

Mastodon/Diffiable/Section/CategoryPickerSection.swift

@@ -0,0 +1,31 @@
+//
+//  CategoryPickerSection.swift
+//  Mastodon
+//
+//  Created by Cirno MainasuK on 2021/3/5.
+//
+
+import UIKit
+
+enum CategoryPickerSection: Equatable, Hashable {
+    case main
+}
+
+extension CategoryPickerSection {
+    static func collectionViewDiffableDataSource(
+        for collectionView: UICollectionView,
+        dependency: NeedsDependency
+    ) -> UICollectionViewDiffableDataSource<CategoryPickerSection, CategoryPickerItem> {
+        UICollectionViewDiffableDataSource(collectionView: collectionView) { collectionView, indexPath, item -> UICollectionViewCell? in
+            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: String(describing: PickServerCategoryCollectionViewCell.self), for: indexPath) as! PickServerCategoryCollectionViewCell
+            switch item {
+            case .all:
+                cell.categoryView.titleLabel.font = .systemFont(ofSize: 17)
+            case .category:
+                cell.categoryView.titleLabel.font = .systemFont(ofSize: 28)
+            }
+            cell.categoryView.titleLabel.text = item.title
+            return cell
+        }
+    }
+}

Mastodon/Diffiable/Section/PickServerItem.swift

@@ -0,0 +1,67 @@
+//
+//  PickServerItem.swift
+//  Mastodon
+//
+//  Created by Cirno MainasuK on 2021/3/5.
+//
+
+import Foundation
+import MastodonSDK
+
+/// Note: update Equatable when change case
+enum PickServerItem {
+    case header
+    case categoryPicker(items: [CategoryPickerItem])
+    case search
+    case server(server: Mastodon.Entity.Server, attribute: ServerItemAttribute)
+}
+
+extension PickServerItem {
+    final class ServerItemAttribute: Equatable, Hashable {
+        var isExpand: Bool
+        
+        init(isExpand: Bool) {
+            self.isExpand = isExpand
+        }
+        
+        static func == (lhs: PickServerItem.ServerItemAttribute, rhs: PickServerItem.ServerItemAttribute) -> Bool {
+            return lhs.isExpand == rhs.isExpand
+        }
+        
+        func hash(into hasher: inout Hasher) {
+            hasher.combine(isExpand)
+        }
+    }
+}
+
+extension PickServerItem: Equatable {
+    static func == (lhs: PickServerItem, rhs: PickServerItem) -> Bool {
+        switch (lhs, rhs) {
+        case (.header, .header):
+            return true
+        case (.categoryPicker(let itemsLeft), .categoryPicker(let itemsRight)):
+            return itemsLeft == itemsRight
+        case (.search, .search):
+            return true
+        case (.server(let serverLeft, _), .server(let serverRight, _)):
+            return serverLeft.domain == serverRight.domain
+        default:
+            return false
+        }
+    }
+}
+
+extension PickServerItem: Hashable {
+    func hash(into hasher: inout Hasher) {
+        switch self {
+        case .header:
+            hasher.combine(String(describing: PickServerItem.header.self))
+        case .categoryPicker(let items):
+            hasher.combine(items)
+        case .search:
+            hasher.combine(String(describing: PickServerItem.search.self))
+        case .server(let server, _):
+            hasher.combine(server.domain)
+        }
+    }
+}

Mastodon/Diffiable/Section/PickServerSection.swift

@@ -0,0 +1,100 @@
+//
+//  PickServerSection.swift
+//  Mastodon
+//
+//  Created by Cirno MainasuK on 2021/3/5.
+//
+
+import UIKit
+import MastodonSDK
+import Kanna
+
+enum PickServerSection: Equatable, Hashable {
+    case header
+    case category
+    case search
+    case servers
+}
+
+extension PickServerSection {
+    static func tableViewDiffableDataSource(
+        for tableView: UITableView,
+        dependency: NeedsDependency,
+        pickServerSearchCellDelegate: PickServerSearchCellDelegate,
+        pickServerCellDelegate: PickServerCellDelegate
+    ) -> UITableViewDiffableDataSource<PickServerSection, PickServerItem> {
+        UITableViewDiffableDataSource(tableView: tableView) { [weak pickServerSearchCellDelegate, weak pickServerCellDelegate] tableView, indexPath, item -> UITableViewCell? in
+            switch item {
+            case .header:
+                let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerTitleCell.self), for: indexPath) as! PickServerTitleCell
+                return cell
+            case .categoryPicker(let items):
+                let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerCategoriesCell.self), for: indexPath) as! PickServerCategoriesCell
+                cell.diffableDataSource = CategoryPickerSection.collectionViewDiffableDataSource(
+                    for: cell.collectionView,
+                    dependency: dependency
+                )
+                var snapshot = NSDiffableDataSourceSnapshot<CategoryPickerSection, CategoryPickerItem>()
+                snapshot.appendSections([.main])
+                snapshot.appendItems(items, toSection: .main)
+                cell.diffableDataSource?.apply(snapshot, animatingDifferences: false, completion: nil)
+                return cell
+            case .search:
+                let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerSearchCell.self), for: indexPath) as! PickServerSearchCell
+                cell.delegate = pickServerSearchCellDelegate
+                return cell
+            case .server(let server, let attribute):
+                let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerCell.self), for: indexPath) as! PickServerCell
+                PickServerSection.configure(cell: cell, server: server, attribute: attribute)
+                cell.delegate = pickServerCellDelegate
+                // cell.server = server
+                //            if expandServerDomainSet.contains(server.domain) {
+                //                cell.mode = .expand
+                //            } else {
+                //                cell.mode = .collapse
+                //            }
+//                if server == viewModel.selectedServer.value {
+//                    tableView.selectRow(at: indexPath, animated: false, scrollPosition: .none)
+//                } else {
+//                    tableView.deselectRow(at: indexPath, animated: false)
+//                }
+//
+//                cell.delegate = self
+                return cell
+            }
+        }
+    }
+}
+
+extension PickServerSection {
+    
+    static func configure(cell: PickServerCell, server: Mastodon.Entity.Server, attribute: PickServerItem.ServerItemAttribute) {
+        cell.domainLabel.text = server.domain
+        cell.descriptionLabel.text = {
+            guard let html = try? HTML(html: server.description, encoding: .utf8) else {
+                return server.description
+            }
+            
+            return html.text ?? server.description
+        }()
+        cell.langValueLabel.text = server.language.uppercased()
+        cell.usersValueLabel.text = parseUsersCount(server.totalUsers)
+        cell.categoryValueLabel.text = server.category.uppercased()
+        
+        cell.updateExpandMode(mode: attribute.isExpand ? .expand : .collapse)
+//        UIView.animate(withDuration: 0.33) {
+//            cell.expandBox.layoutIfNeeded()
+//        }
+    }
+    
+    private static func parseUsersCount(_ usersCount: Int) -> String {
+        switch usersCount {
+        case 0..<1000:
+            return "\(usersCount)"
+        default:
+            let usersCountInThousand = Float(usersCount) / 1000.0
+            return String(format: "%.1fK", usersCountInThousand)
+        }
+    }
+    
+}

Mastodon/Scene/Onboarding/PickServer/CollectionViewCell/PickServerCategoryCollectionViewCell.swift

@@ -9,12 +9,6 @@ import UIKit
 
 class PickServerCategoryCollectionViewCell: UICollectionViewCell {
     
-    var category: MastodonPickServerViewModel.Category? {
-        didSet {
-            categoryView.category = category
-        }
-    }
-    
     var categoryView: PickServerCategoryView = {
         let view = PickServerCategoryView()
         view.translatesAutoresizingMaskIntoConstraints = false

Mastodon/Scene/Onboarding/PickServer/MastodonPickServerViewController.swift

@@ -5,10 +5,9 @@
 //  Created by BradGao on 2021/2/20.
 //
 
+import os.log
 import UIKit
 import Combine
-import OSLog
-import MastodonSDK
 
 final class MastodonPickServerViewController: UIViewController, NeedsDependency {
     
@@ -22,13 +21,6 @@ final class MastodonPickServerViewController: UIViewController, NeedsDependency
     private var isAuthenticating = CurrentValueSubject<Bool, Never>(false)
     
     private var expandServerDomainSet = Set<String>()
-    
-    enum Section: CaseIterable {
-        case title
-        case categories
-        case search
-        case serverList
-    }
 
     let tableView: UITableView = {
         let tableView = ControlContainableTableView()
@@ -95,31 +87,16 @@ extension MastodonPickServerViewController {
         nextStepButton.addTarget(self, action: #selector(nextStepButtonDidClicked(_:)), for: .touchUpInside)
         
         tableView.delegate = self
-        tableView.dataSource = self
+        viewModel.setupDiffableDataSource(
-        
+            for: tableView,
-        viewModel
+            dependency: self,
-            .searchedServers
+            pickServerSearchCellDelegate: self,
-            .receive(on: DispatchQueue.main)
+            pickServerCellDelegate: self
-            .sink { _ in
+        )
-                
-            } receiveValue: { [weak self] servers in
-                self?.tableView.beginUpdates()
-                self?.tableView.reloadSections(IndexSet(integer: 3), with: .automatic)
-                self?.tableView.endUpdates()
-                if let selectedServer = self?.viewModel.selectedServer.value, servers.contains(selectedServer) {
-                    // Previously selected server is still in the list, do nothing
-                } else {
-                    // Previously selected server is not in the updated list, reset the selectedServer's value
-                    self?.viewModel.selectedServer.send(nil)
-                }
-            }
-            .store(in: &disposeBag)
         
         viewModel
             .selectedServer
-            .map {
+            .map { $0 != nil }
-                $0 != nil
-            }
             .assign(to: \.isEnabled, on: nextStepButton)
             .store(in: &disposeBag)
         
@@ -165,8 +142,6 @@ extension MastodonPickServerViewController {
                 isAuthenticating ? self.nextStepButton.showLoading() : self.nextStepButton.stopLoading()
             }
             .store(in: &disposeBag)
-        
-        viewModel.fetchAllServers()
     }
     
     @objc
@@ -292,142 +267,150 @@ extension MastodonPickServerViewController {
 }
 
 extension MastodonPickServerViewController: UITableViewDelegate {
+    
+    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
+        return UIView()
+    }
+    
     func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
-        let category = Section.allCases[section]
+        guard let diffableDataSource = viewModel.diffableDataSource else { return 0 }
-        switch category {
+        let sections = diffableDataSource.snapshot().sectionIdentifiers
-        case .title:
+        let section = sections[section]
+        switch section {
+        case .header:
             return 20
-        case .categories:
+        case .category:
             // Since category view has a blur shadow effect, its height need to be large than the actual height,
             // Thus we reduce the section header's height by 10, and make the category cell height 60+20(10 inset for top and bottom)
             return 10
         case .search:
             // Same reason as above
             return 10
-        case .serverList:
+        case .servers:
             return 0
         }
     }
     
     func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
+        guard let diffableDataSource = viewModel.diffableDataSource else { return nil }
+        guard let item = diffableDataSource.itemIdentifier(for: indexPath) else { return nil }
+        guard case let .server(server) = item else { return nil }
+        
         if tableView.indexPathForSelectedRow == indexPath {
             tableView.deselectRow(at: indexPath, animated: false)
             viewModel.selectedServer.send(nil)
             return nil
         }
+        
         return indexPath
     }
     
     func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
+        guard let diffableDataSource = viewModel.diffableDataSource else { return }
+        guard let item = diffableDataSource.itemIdentifier(for: indexPath) else { return }
+        guard case let .server(server, _) = item else { return }
         tableView.selectRow(at: indexPath, animated: false, scrollPosition: .none)
-        viewModel.selectedServer.send(viewModel.searchedServers.value[indexPath.row])
+        viewModel.selectedServer.send(server)
     }
-    
+
     func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
         tableView.deselectRow(at: indexPath, animated: false)
         viewModel.selectedServer.send(nil)
     }
+    
 }
 
-extension MastodonPickServerViewController: UITableViewDataSource {
+//extension MastodonPickServerViewController: UITableViewDataSource {
-    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
-        return UIView()
-    }
-    
-    func numberOfSections(in tableView: UITableView) -> Int {
-        return Self.Section.allCases.count
-    }
-    
-    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-        let section = Self.Section.allCases[section]
-        switch section {
-        case .title,
-             .categories,
-             .search:
-            return 1
-        case .serverList:
-            return viewModel.searchedServers.value.count
-        }
-    }
-    
-    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
-        
-        let section = Self.Section.allCases[indexPath.section]
-        switch section {
-        case .title:
-            let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerTitleCell.self), for: indexPath) as! PickServerTitleCell
-            return cell
-        case .categories:
-            let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerCategoriesCell.self), for: indexPath) as! PickServerCategoriesCell
-            cell.dataSource = self
-            cell.delegate = self
-            return cell
-        case .search:
-            let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerSearchCell.self), for: indexPath) as! PickServerSearchCell
-            cell.delegate = self
-            return cell
-        case .serverList:
-            let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerCell.self), for: indexPath) as! PickServerCell
-            let server = viewModel.searchedServers.value[indexPath.row]
-            cell.server = server
-            if expandServerDomainSet.contains(server.domain) {
-                cell.mode = .expand
-            } else {
-                cell.mode = .collapse
-            }
-            if server == viewModel.selectedServer.value {
-                tableView.selectRow(at: indexPath, animated: false, scrollPosition: .none)
-            } else {
-                tableView.deselectRow(at: indexPath, animated: false)
-            }
-            
-            cell.delegate = self
-            return cell
-        }
-    }
-}
 
-extension MastodonPickServerViewController: PickServerCellDelegate {
+//    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
-    func pickServerCell(modeChange server: Mastodon.Entity.Server, newMode: PickServerCell.Mode, updates: (() -> Void)) {
+//
-        if newMode == .collapse {
+//        let section = Self.Section.allCases[indexPath.section]
-            expandServerDomainSet.remove(server.domain)
+//        switch section {
-        } else {
+//        case .title:
-            expandServerDomainSet.insert(server.domain)
+//
-        }
+//        case .categories:
-        
+//
-        tableView.beginUpdates()
+//        case .search:
-        updates()
+//
-        tableView.endUpdates()
+//        case .serverList:
-        
+//            let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PickServerCell.self), for: indexPath) as! PickServerCell
-        if newMode == .expand, let modeChangeIndex = self.viewModel.searchedServers.value.firstIndex(where: { $0 == server }), self.tableView.indexPathsForVisibleRows?.last?.row == modeChangeIndex {
+//            let server = viewModel.servers.value[indexPath.row]
-            self.tableView.scrollToRow(at: IndexPath(row: modeChangeIndex, section: 3), at: .bottom, animated: true)
+//            // cell.server = server
-        }
+////            if expandServerDomainSet.contains(server.domain) {
-    }
+////                cell.mode = .expand
-}
+////            } else {
+////                cell.mode = .collapse
+////            }
+//            if server == viewModel.selectedServer.value {
+//                tableView.selectRow(at: indexPath, animated: false, scrollPosition: .none)
+//            } else {
+//                tableView.deselectRow(at: indexPath, animated: false)
+//            }
+//
+//            cell.delegate = self
+//            return cell
+//        }
+//    }
+//}
 
+// MARK: - PickServerSearchCellDelegate
 extension MastodonPickServerViewController: PickServerSearchCellDelegate {
-    func pickServerSearchCell(didChange searchText: String?) {
+    func pickServerSearchCell(_ cell: PickServerSearchCell, searchTextDidChange searchText: String?) {
         viewModel.searchText.send(searchText)
     }
 }
 
-extension MastodonPickServerViewController: PickServerCategoriesDataSource, PickServerCategoriesDelegate {
+// MARK: - PickServerCellDelegate
-    func numberOfCategories() -> Int {
+extension MastodonPickServerViewController: PickServerCellDelegate {
-        return viewModel.categories.count
+    func pickServerCell(_ cell: PickServerCell, expandButtonPressed button: UIButton) {
-    }
+        guard let diffableDataSource = viewModel.diffableDataSource else { return }
-    
+        guard let indexPath = tableView.indexPath(for: cell) else { return }
-    func category(at index: Int) -> MastodonPickServerViewModel.Category {
+        guard let item = diffableDataSource.itemIdentifier(for: indexPath) else { return }
-        return viewModel.categories[index]
+        guard case let .server(_, attribute) = item else { return }
-    }
+        
-    
+        attribute.isExpand.toggle()
-    func selectedIndex() -> Int {
+        tableView.beginUpdates()
-        return viewModel.selectCategoryIndex.value
+        cell.updateExpandMode(mode: attribute.isExpand ? .expand : .collapse)
-    }
+        tableView.endUpdates()
-    
+        
-    func pickServerCategoriesCell(didSelect index: Int) {
+        // expand attribute change do not needs apply snapshot to diffable data source
-        return viewModel.selectCategoryIndex.send(index)
+        // but should I block the viewModel data binding during tableView.beginUpdates/endUpdates?
     }
+
+//    func pickServerCell(modeChange server: Mastodon.Entity.Server, newMode: PickServerCell.Mode, updates: (() -> Void)) {
+//        if newMode == .collapse {
+//            expandServerDomainSet.remove(server.domain)
+//        } else {
+//            expandServerDomainSet.insert(server.domain)
+//        }
+//
+//        tableView.beginUpdates()
+//        updates()
+//        tableView.endUpdates()
+//
+//        if newMode == .expand, let modeChangeIndex = self.viewModel.servers.value.firstIndex(where: { $0 == server }), self.tableView.indexPathsForVisibleRows?.last?.row == modeChangeIndex {
+//            self.tableView.scrollToRow(at: IndexPath(row: modeChangeIndex, section: 3), at: .bottom, animated: true)
+//        }
+//    }
 }
 
+//extension MastodonPickServerViewController: PickServerCategoriesDataSource, PickServerCategoriesCellDelegate {
+//    func numberOfCategories() -> Int {
+//        return viewModel.categories.count
+//    }
+//    
+//    func category(at index: Int) -> MastodonPickServerViewModel.Category {
+//        return viewModel.categories[index]
+//    }
+//    
+//    func selectedIndex() -> Int {
+//        return viewModel.selectCategoryIndex.value
+//    }
+//    
+//    func pickServerCategoriesCell(_ cell: PickServerCategoriesCell, didSelect index: Int) {
+//        return viewModel.selectCategoryIndex.send(index)
+//    }
+//}
+
 // MARK: - OnboardingViewControllerAppearance
 extension MastodonPickServerViewController: OnboardingViewControllerAppearance { }

Mastodon/Scene/Onboarding/PickServer/MastodonPickServerViewModel+Diffable.swift

@@ -0,0 +1,37 @@
+//
+//  MastodonPickServerViewController+Diffable.swift
+//  Mastodon
+//
+//  Created by Cirno MainasuK on 2021/3/5.
+//
+
+import UIKit
+
+extension MastodonPickServerViewModel {
+    
+    func setupDiffableDataSource(
+        for tableView: UITableView,
+        dependency: NeedsDependency,
+        pickServerSearchCellDelegate: PickServerSearchCellDelegate,
+        pickServerCellDelegate: PickServerCellDelegate
+    ) {
+        diffableDataSource = PickServerSection.tableViewDiffableDataSource(
+            for: tableView,
+            dependency: dependency,
+            pickServerSearchCellDelegate: pickServerSearchCellDelegate,
+            pickServerCellDelegate: pickServerCellDelegate
+        )
+        
+        var snapshot = NSDiffableDataSourceSnapshot<PickServerSection, PickServerItem>()
+        snapshot.appendSections([.header, .category, .search, .servers])
+        snapshot.appendItems([.header], toSection: .header)
+        snapshot.appendItems([.categoryPicker(items: categoryPickerItems)], toSection: .category)
+        snapshot.appendItems([.search], toSection: .search)
+        diffableDataSource?.apply(snapshot, animatingDifferences: false, completion: nil)
+        
+        loadIndexedServerStateMachine.enter(LoadIndexedServerState.Loading.self)
+    }
+    
+}
+
+

Mastodon/Scene/Onboarding/PickServer/MastodonPickServerViewModel+LoadIndexedServerState.swift

@@ -0,0 +1,84 @@
+//
+//  MastodonPickServerViewModel+LoadIndexedServerState.swift
+//  Mastodon
+//
+//  Created by Cirno MainasuK on 2021/3/5.
+//
+
+import os.log
+import Foundation
+import GameplayKit
+import MastodonSDK
+
+extension MastodonPickServerViewModel {
+    class LoadIndexedServerState: GKState {
+        weak var viewModel: MastodonPickServerViewModel?
+        
+        init(viewModel: MastodonPickServerViewModel) {
+            self.viewModel = viewModel
+        }
+        
+        override func didEnter(from previousState: GKState?) {
+            os_log("%{public}s[%{public}ld], %{public}s: enter %s, previous: %s", ((#file as NSString).lastPathComponent), #line, #function, self.debugDescription, previousState.debugDescription)
+        }
+    }
+}
+
+extension MastodonPickServerViewModel.LoadIndexedServerState {
+
+    class Initial: MastodonPickServerViewModel.LoadIndexedServerState {
+        override func isValidNextState(_ stateClass: AnyClass) -> Bool {
+            return stateClass == Loading.self
+        }
+    }
+    
+    class Loading: MastodonPickServerViewModel.LoadIndexedServerState {
+        override func isValidNextState(_ stateClass: AnyClass) -> Bool {
+            return stateClass == Fail.self || stateClass == Idle.self
+        }
+        
+        override func didEnter(from previousState: GKState?) {
+            super.didEnter(from: previousState)
+            
+            guard let viewModel = self.viewModel, let stateMachine = self.stateMachine else { return }
+            viewModel.context.apiService.servers(language: nil, category: nil)
+                .sink { completion in
+                    switch completion {
+                    case .failure(let error):
+                        // TODO: handle error
+                        break
+                    case .finished:
+                        break
+                    }
+                } receiveValue: { [weak self] response in
+                    guard let _ = self else { return }
+                    stateMachine.enter(Idle.self)
+                    viewModel.indexedServers.value = response.value
+                }
+                .store(in: &viewModel.disposeBag)
+        }
+    }
+    
+    class Fail: MastodonPickServerViewModel.LoadIndexedServerState {
+        override func isValidNextState(_ stateClass: AnyClass) -> Bool {
+            return stateClass == Loading.self
+        }
+        
+        override func didEnter(from previousState: GKState?) {
+            super.didEnter(from: previousState)
+            
+            guard let viewModel = self.viewModel, let stateMachine = self.stateMachine else { return }
+            DispatchQueue.main.asyncAfter(deadline: .now() + 3) { [weak self] in
+                guard let self = self else { return }
+                stateMachine.enter(Loading.self)
+            }
+        }
+    }
+    
+    class Idle: MastodonPickServerViewModel.LoadIndexedServerState {
+        override func isValidNextState(_ stateClass: AnyClass) -> Bool {
+            return false
+        }
+    }
+
+}

Mastodon/Scene/Onboarding/PickServer/MastodonPickServerViewModel.swift

@@ -5,9 +5,10 @@
 //  Created by BradGao on 2021/2/23.
 //
 
+import os.log
 import UIKit
-import OSLog
 import Combine
+import GameplayKit
 import MastodonSDK
 import CoreDataStack
 
@@ -17,69 +18,41 @@ class MastodonPickServerViewModel: NSObject {
         case signIn
     }
     
-    enum Category {
+    var disposeBag = Set<AnyCancellable>()
-        // `all` means search for all categories
+
-        case all
+    // input
-        // `some` means search for specific category
-        case some(Mastodon.Entity.Category)
-        
-        var title: String {
-            switch self {
-            case .all:
-                return L10n.Scene.ServerPicker.Button.Category.all
-            case .some(let masCategory):
-                // TODO: Use emoji as placeholders
-                switch masCategory.category {
-                case .academia:
-                    return "📚"
-                case .activism:
-                    return "✊"
-                case .food:
-                    return "🍕"
-                case .furry:
-                    return "🦁"
-                case .games:
-                    return "🕹"
-                case .general:
-                    return "GE"
-                case .journalism:
-                    return "📰"
-                case .lgbt:
-                    return "🏳️‍🌈"
-                case .regional:
-                    return "📍"
-                case .art:
-                    return "🎨"
-                case .music:
-                    return "🎼"
-                case .tech:
-                    return "📱"
-                case ._other:
-                    return "❓"
-                }
-            }
-        }
-    }
-    
     let mode: PickServerMode
     let context: AppContext
-    
+    var categoryPickerItems: [CategoryPickerItem] = {
-    var categories = [Category]()
+        var items: [CategoryPickerItem] = []
+        items.append(.all)
+        items.append(contentsOf: APIService.stubCategories().map { CategoryPickerItem.category(category: $0) })
+        return items
+    }()
     let selectCategoryIndex = CurrentValueSubject<Int, Never>(0)
-    
     let searchText = CurrentValueSubject<String?, Never>(nil)
+    let indexedServers = CurrentValueSubject<[Mastodon.Entity.Server], Never>([])
+    let unindexedServers = CurrentValueSubject<[Mastodon.Entity.Instance], Never>([])
     
-    let allServers = CurrentValueSubject<[Mastodon.Entity.Server], Never>([])
+    // output
-    let searchedServers = CurrentValueSubject<[Mastodon.Entity.Server], Error>([])
+    var diffableDataSource: UITableViewDiffableDataSource<PickServerSection, PickServerItem>?
+    private(set) lazy var loadIndexedServerStateMachine: GKStateMachine = {
+        // exclude timeline middle fetcher state
+        let stateMachine = GKStateMachine(states: [
+            LoadIndexedServerState.Initial(viewModel: self),
+            LoadIndexedServerState.Loading(viewModel: self),
+            LoadIndexedServerState.Fail(viewModel: self),
+            LoadIndexedServerState.Idle(viewModel: self),
+        ])
+        stateMachine.enter(LoadIndexedServerState.Initial.self)
+        return stateMachine
+    }()
     
+    let servers = CurrentValueSubject<[Mastodon.Entity.Server], Error>([])
     let selectedServer = CurrentValueSubject<Mastodon.Entity.Server?, Never>(nil)
     let error = PassthroughSubject<Error, Never>()
     let authenticated = PassthroughSubject<(domain: String, account: Mastodon.Entity.Account), Never>()
-    
+        
-    private var disposeBag = Set<AnyCancellable>()
-    
-    weak var tableView: UITableView?
-    
     var mastodonPinBasedAuthenticationViewController: UIViewController?
     
     init(context: AppContext, mode: PickServerMode) {
@@ -91,83 +64,115 @@ class MastodonPickServerViewModel: NSObject {
     }
     
     private func configure() {
-        let masCategories = context.apiService.stubCategories()
-        categories.append(.all)
-        categories.append(contentsOf: masCategories.map { Category.some($0) })
-        
         Publishers.CombineLatest3(
-            selectCategoryIndex,
+            indexedServers,
-            searchText.debounce(for: .milliseconds(300), scheduler: DispatchQueue.main).removeDuplicates(),
+            unindexedServers,
-            allServers
+            searchText
         )
-        .flatMap { [weak self] (selectCategoryIndex, searchText, allServers) -> AnyPublisher<Result<[Mastodon.Entity.Server], Error>, Never> in
+        .receive(on: DispatchQueue.main)
-            guard let self = self else { return Just(Result.success([])).eraseToAnyPublisher() }
+        .sink(receiveValue: { [weak self] indexedServers, unindexedServers, searchText in
+            guard let self = self else { return }
+            guard let diffableDataSource = self.diffableDataSource else { return }
             
-            // 1. Search from the servers recorded in joinmastodon.org
+            let oldSnapshot = diffableDataSource.snapshot()
-            let searchedServersFromAPI = self.searchServersFromAPI(category: self.categories[selectCategoryIndex], searchText: searchText, allServers: allServers)
+            var oldSnapshotServerItemAttributeDict: [String : PickServerItem.ServerItemAttribute] = [:]
-            if !searchedServersFromAPI.isEmpty {
+            for item in oldSnapshot.itemIdentifiers {
-                // If found servers, just return
+                guard case let .server(server, attribute) = item else { continue }
-                return Just(Result.success(searchedServersFromAPI)).eraseToAnyPublisher()
+                oldSnapshotServerItemAttributeDict[server.domain] = attribute
-            }
-            // 2. No server found in the recorded list, check if searchText is a valid mastodon server domain
-            if let toSearchText = searchText, !toSearchText.isEmpty, let _ = URL(string: "https://\(toSearchText)") {
-                return self.context.apiService.instance(domain: toSearchText)
-                    .map { return Result.success([Mastodon.Entity.Server(instance: $0.value)]) }
-                    .catch({ error -> Just<Result<[Mastodon.Entity.Server], Error>> in
-                        return Just(Result.failure(error))
-                    })
-                    .eraseToAnyPublisher()
-            }
-            return Just(Result.success(searchedServersFromAPI)).eraseToAnyPublisher()
-        }
-        .sink { _ in
-            
-        } receiveValue: { [weak self] result in
-            switch result {
-            case .success(let servers):
-                self?.searchedServers.send(servers)
-            case .failure(let error):
-                // TODO: What should be presented when user inputs invalid search text?
-                self?.searchedServers.send([])
             }
             
-        }
+            var snapshot = NSDiffableDataSourceSnapshot<PickServerSection, PickServerItem>()
+            snapshot.appendSections([.header, .category, .search, .servers])
+            snapshot.appendItems([.header], toSection: .header)
+            snapshot.appendItems([.categoryPicker(items: self.categoryPickerItems)], toSection: .category)
+            snapshot.appendItems([.search], toSection: .search)
+            // TODO: handle filter
+            var serverItems: [PickServerItem] = []
+            for server in indexedServers {
+                let attribute = oldSnapshotServerItemAttributeDict[server.domain] ?? PickServerItem.ServerItemAttribute(isExpand: false)
+                let item = PickServerItem.server(server: server, attribute: attribute)
+                serverItems.append(item)
+            }
+            snapshot.appendItems(serverItems, toSection: .servers)
+            
+            diffableDataSource.apply(snapshot)
+        })
         .store(in: &disposeBag)
+        
+        
+//        Publishers.CombineLatest3(
+//            selectCategoryIndex,
+//            searchText.debounce(for: .milliseconds(300), scheduler: DispatchQueue.main).removeDuplicates(),
+//            indexedServers
+//        )
+//        .flatMap { [weak self] (selectCategoryIndex, searchText, allServers) -> AnyPublisher<Result<[Mastodon.Entity.Server], Error>, Never> in
+//            guard let self = self else { return Just(Result.success([])).eraseToAnyPublisher() }
+//
+//            // 1. Search from the servers recorded in joinmastodon.org
+//            let searchedServersFromAPI = self.searchServersFromAPI(category: self.categories[selectCategoryIndex], searchText: searchText, allServers: allServers)
+//            if !searchedServersFromAPI.isEmpty {
+//                // If found servers, just return
+//                return Just(Result.success(searchedServersFromAPI)).eraseToAnyPublisher()
+//            }
+//            // 2. No server found in the recorded list, check if searchText is a valid mastodon server domain
+//            if let toSearchText = searchText, !toSearchText.isEmpty, let _ = URL(string: "https://\(toSearchText)") {
+//                return self.context.apiService.instance(domain: toSearchText)
+//                    .map { return Result.success([Mastodon.Entity.Server(instance: $0.value)]) }
+//                    .catch({ error -> Just<Result<[Mastodon.Entity.Server], Error>> in
+//                        return Just(Result.failure(error))
+//                    })
+//                    .eraseToAnyPublisher()
+//            }
+//            return Just(Result.success(searchedServersFromAPI)).eraseToAnyPublisher()
+//        }
+//        .sink { _ in
+//
+//        } receiveValue: { [weak self] result in
+//            switch result {
+//            case .success(let servers):
+//                self?.servers.send(servers)
+//            case .failure(let error):
+//                // TODO: What should be presented when user inputs invalid search text?
+//                self?.servers.send([])
+//            }
+//
+//        }
+//        .store(in: &disposeBag)
 
         
     }
     
-    func fetchAllServers() {
+//    func fetchAllServers() {
-        context.apiService.servers(language: nil, category: nil)
+//        context.apiService.servers(language: nil, category: nil)
-            .sink { completion in
+//            .sink { completion in
-                // TODO: Add a reload button when fails to fetch servers initially
+//                // TODO: Add a reload button when fails to fetch servers initially
-            } receiveValue: { [weak self] result in
+//            } receiveValue: { [weak self] result in
-                self?.allServers.send(result.value)
+//                self?.indexedServers.send(result.value)
-            }
+//            }
-            .store(in: &disposeBag)
+//            .store(in: &disposeBag)
-        
+//        
-    }
+//    }
-    
+//    
-    private func searchServersFromAPI(category: Category, searchText: String?, allServers: [Mastodon.Entity.Server]) -> [Mastodon.Entity.Server] {
+//    private func searchServersFromAPI(category: Category, searchText: String?, allServers: [Mastodon.Entity.Server]) -> [Mastodon.Entity.Server] {
-        return allServers
+//        return allServers
-            // 1. Filter the category
+//            // 1. Filter the category
-            .filter {
+//            .filter {
-                switch category {
+//                switch category {
-                case .all:
+//                case .all:
-                    return true
+//                    return true
-                case .some(let masCategory):
+//                case .some(let masCategory):
-                    return $0.category.caseInsensitiveCompare(masCategory.category.rawValue) == .orderedSame
+//                    return $0.category.caseInsensitiveCompare(masCategory.category.rawValue) == .orderedSame
-                }
+//                }
-            }
+//            }
-            // 2. Filter the searchText
+//            // 2. Filter the searchText
-            .filter {
+//            .filter {
-                if let searchText = searchText, !searchText.isEmpty {
+//                if let searchText = searchText, !searchText.isEmpty {
-                    return $0.domain.lowercased().contains(searchText.lowercased())
+//                    return $0.domain.lowercased().contains(searchText.lowercased())
-                } else {
+//                } else {
-                    return true
+//                    return true
-                }
+//                }
-            }
+//            }
-    }
+//    }
 }
 
 // MARK: - SignIn methods & structs

Mastodon/Scene/Onboarding/PickServer/TableViewCell/PickServerCategoriesCell.swift

@@ -5,24 +5,20 @@
 //  Created by BradGao on 2021/2/23.
 //
 
+import os.log
 import UIKit
 import MastodonSDK
 
-protocol PickServerCategoriesDataSource: class {
+protocol PickServerCategoriesCellDelegate: class {
-    func numberOfCategories() -> Int
+    func pickServerCategoriesCell(_ cell: PickServerCategoriesCell, collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
-    func category(at index: Int) -> MastodonPickServerViewModel.Category
-    func selectedIndex() -> Int
-}
-
-protocol PickServerCategoriesDelegate: class {
-    func pickServerCategoriesCell(didSelect index: Int)
 }
 
 final class PickServerCategoriesCell: UITableViewCell {
     
-    weak var dataSource: PickServerCategoriesDataSource!
+    weak var delegate: PickServerCategoriesCellDelegate?
-    weak var delegate: PickServerCategoriesDelegate!
     
+    var diffableDataSource: UICollectionViewDiffableDataSource<CategoryPickerSection, CategoryPickerItem>?
+        
     let metricView = UIView()
     
     let collectionView: UICollectionView = {
@@ -38,6 +34,12 @@ final class PickServerCategoriesCell: UITableViewCell {
         return view
     }()
     
+    override func prepareForReuse() {
+        super.prepareForReuse()
+        
+        delegate = nil
+    }
+    
     override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
         super.init(style: style, reuseIdentifier: reuseIdentifier)
         _init()
@@ -75,7 +77,6 @@ extension PickServerCategoriesCell {
         ])
         
         collectionView.delegate = self
-        collectionView.dataSource = self
     }
     
     override func layoutSubviews() {
@@ -86,45 +87,46 @@ extension PickServerCategoriesCell {
 
 }
 
+// MARK: - UICollectionViewDelegateFlowLayout
 extension PickServerCategoriesCell: UICollectionViewDelegateFlowLayout {
     func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
         collectionView.selectItem(at: indexPath, animated: true, scrollPosition: .centeredHorizontally)
-        delegate.pickServerCategoriesCell(didSelect: indexPath.row)
+//        delegate.pickServerCategoriesCell(self, didSelect: indexPath.row)
     }
-    
+
     func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
         layoutIfNeeded()
         return UIEdgeInsets(top: 0, left: metricView.frame.minX - collectionView.frame.minX, bottom: 0, right: collectionView.frame.maxX - metricView.frame.maxX)
     }
-    
+
     func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
         return 16
     }
-    
+
     func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
         return CGSize(width: 60, height: 80)
     }
 }
 
-extension PickServerCategoriesCell: UICollectionViewDataSource {
+//extension PickServerCategoriesCell: UICollectionViewDataSource {
-    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
+//    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
-        return dataSource.numberOfCategories()
+//        return dataSource.numberOfCategories()
-    }
+//    }
-    
+//
-    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
+//    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
-        let category = dataSource.category(at: indexPath.row)
+//        let category = dataSource.category(at: indexPath.row)
-        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: String(describing: PickServerCategoryCollectionViewCell.self), for: indexPath) as! PickServerCategoryCollectionViewCell
+//        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: String(describing: PickServerCategoryCollectionViewCell.self), for: indexPath) as! PickServerCategoryCollectionViewCell
-        cell.category = category
+//        cell.category = category
-        
+//
-        // Select the default category by default
+//        // Select the default category by default
-        if indexPath.row == dataSource.selectedIndex() {
+//        if indexPath.row == dataSource.selectedIndex() {
-            // Use `[]` as the scrollPosition to avoid contentOffset change
+//            // Use `[]` as the scrollPosition to avoid contentOffset change
-            collectionView.selectItem(at: indexPath, animated: false, scrollPosition: [])
+//            collectionView.selectItem(at: indexPath, animated: false, scrollPosition: [])
-            cell.isSelected = true
+//            cell.isSelected = true
-        }
+//        }
-        return cell
+//        return cell
-    }
+//    }
-    
+//
-    
+//
-}
+//}
 

Mastodon/Scene/Onboarding/PickServer/TableViewCell/PickServerCell.swift

@@ -5,25 +5,21 @@
 //  Created by BradGao on 2021/2/24.
 //
 
+import os.log
 import UIKit
 import MastodonSDK
 import AlamofireImage
 import Kanna
 
 protocol PickServerCellDelegate: class {
-    func pickServerCell(modeChange server: Mastodon.Entity.Server, newMode: PickServerCell.Mode, updates: (() -> Void))
+    func pickServerCell(_ cell: PickServerCell, expandButtonPressed button: UIButton)
 }
 
 class PickServerCell: UITableViewCell {
     
     weak var delegate: PickServerCellDelegate?
     
-    enum Mode {
+    let containerView: UIView = {
-        case collapse
-        case expand
-    }
-    
-    private var containerView: UIView = {
         let view = UIView()
         view.layoutMargins = UIEdgeInsets(top: 16, left: 16, bottom: 10, right: 16)
         view.backgroundColor = Asset.Colors.lightWhite.color
@@ -31,7 +27,7 @@ class PickServerCell: UITableViewCell {
         return view
     }()
     
-    private var domainLabel: UILabel = {
+    let domainLabel: UILabel = {
         let label = UILabel()
         label.font = .preferredFont(forTextStyle: .headline)
         label.textColor = Asset.Colors.lightDarkGray.color
@@ -40,7 +36,7 @@ class PickServerCell: UITableViewCell {
         return label
     }()
     
-    private var checkbox: UIImageView = {
+    let checkbox: UIImageView = {
         let imageView = UIImageView()
         imageView.preferredSymbolConfiguration = UIImage.SymbolConfiguration(textStyle: .body)
         imageView.tintColor = Asset.Colors.lightSecondaryText.color
@@ -49,7 +45,7 @@ class PickServerCell: UITableViewCell {
         return imageView
     }()
     
-    private var descriptionLabel: UILabel = {
+    let descriptionLabel: UILabel = {
         let label = UILabel()
         label.font = .preferredFont(forTextStyle: .subheadline)
         label.numberOfLines = 0
@@ -59,9 +55,9 @@ class PickServerCell: UITableViewCell {
         return label
     }()
     
-    private let thumbnailActivityIdicator = UIActivityIndicatorView(style: .medium)
+    let thumbnailActivityIdicator = UIActivityIndicatorView(style: .medium)
     
-    private var thumbnailImageView: UIImageView = {
+    let thumbnailImageView: UIImageView = {
         let imageView = UIImageView()
         imageView.clipsToBounds = true
         imageView.contentMode = .scaleAspectFill
@@ -69,7 +65,7 @@ class PickServerCell: UITableViewCell {
         return imageView
     }()
     
-    private var infoStackView: UIStackView = {
+    let infoStackView: UIStackView = {
         let stackView = UIStackView()
         stackView.axis = .horizontal
         stackView.alignment = .fill
@@ -78,14 +74,14 @@ class PickServerCell: UITableViewCell {
         return stackView
     }()
     
-    private var expandBox: UIView = {
+    let expandBox: UIView = {
         let view = UIView()
         view.backgroundColor = .clear
         view.translatesAutoresizingMaskIntoConstraints = false
         return view
     }()
     
-    private var expandButton: UIButton = {
+    let expandButton: UIButton = {
         let button = UIButton(type: .custom)
         button.setTitle(L10n.Scene.ServerPicker.Button.seemore, for: .normal)
         button.setTitle(L10n.Scene.ServerPicker.Button.seeless, for: .selected)
@@ -95,14 +91,14 @@ class PickServerCell: UITableViewCell {
         return button
     }()
     
-    private var seperator: UIView = {
+    let seperator: UIView = {
         let view = UIView()
         view.backgroundColor = Asset.Colors.lightBackground.color
         view.translatesAutoresizingMaskIntoConstraints = false
         return view
     }()
     
-    private var langValueLabel: UILabel = {
+    let langValueLabel: UILabel = {
         let label = UILabel()
         label.textColor = Asset.Colors.lightDarkGray.color
         label.font = UIFontMetrics(forTextStyle: .title2).scaledFont(for: UIFont.systemFont(ofSize: 22, weight: .semibold))
@@ -112,7 +108,7 @@ class PickServerCell: UITableViewCell {
         return label
     }()
     
-    private var usersValueLabel: UILabel = {
+    let usersValueLabel: UILabel = {
         let label = UILabel()
         label.textColor = Asset.Colors.lightDarkGray.color
         label.font = UIFontMetrics(forTextStyle: .title2).scaledFont(for: UIFont.systemFont(ofSize: 22, weight: .semibold))
@@ -122,7 +118,7 @@ class PickServerCell: UITableViewCell {
         return label
     }()
     
-    private var categoryValueLabel: UILabel = {
+    let categoryValueLabel: UILabel = {
         let label = UILabel()
         label.textColor = Asset.Colors.lightDarkGray.color
         label.font = UIFontMetrics(forTextStyle: .title2).scaledFont(for: UIFont.systemFont(ofSize: 22, weight: .semibold))
@@ -132,7 +128,7 @@ class PickServerCell: UITableViewCell {
         return label
     }()
     
-    private var langTitleLabel: UILabel = {
+    let langTitleLabel: UILabel = {
         let label = UILabel()
         label.textColor = Asset.Colors.lightDarkGray.color
         label.font = .preferredFont(forTextStyle: .caption2)
@@ -143,7 +139,7 @@ class PickServerCell: UITableViewCell {
         return label
     }()
     
-    private var usersTitleLabel: UILabel = {
+    let usersTitleLabel: UILabel = {
         let label = UILabel()
         label.textColor = Asset.Colors.lightDarkGray.color
         label.font = .preferredFont(forTextStyle: .caption2)
@@ -154,7 +150,7 @@ class PickServerCell: UITableViewCell {
         return label
     }()
     
-    private var categoryTitleLabel: UILabel = {
+    let categoryTitleLabel: UILabel = {
         let label = UILabel()
         label.textColor = Asset.Colors.lightDarkGray.color
         label.font = .preferredFont(forTextStyle: .caption2)
@@ -168,22 +164,12 @@ class PickServerCell: UITableViewCell {
     private var collapseConstraints: [NSLayoutConstraint] = []
     private var expandConstraints: [NSLayoutConstraint] = []
     
-    var mode: PickServerCell.Mode = .collapse {
-        didSet {
-            updateMode()
-        }
-    }
-    
-    var server: Mastodon.Entity.Server? {
-        didSet {
-            updateServerInfo()
-        }
-    }
-    
     override func prepareForReuse() {
         super.prepareForReuse()
         
+        thumbnailImageView.isHidden = false
         thumbnailImageView.af.cancelImageRequest()
+        thumbnailActivityIdicator.stopAnimating()
     }
     
     override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
@@ -195,6 +181,7 @@ class PickServerCell: UITableViewCell {
         super.init(coder: coder)
         _init()
     }
+    
 }
 
 // MARK: - Methods to configure appearance
@@ -224,7 +211,7 @@ extension PickServerCell {
         infoStackView.addArrangedSubview(verticalInfoStackViewUsers)
         infoStackView.addArrangedSubview(verticalInfoStackViewCategory)
         
-        let expandButtonTopConstraintInCollapse = expandButton.topAnchor.constraint(equalTo: descriptionLabel.lastBaselineAnchor, constant: 12).priority(.required)
+        let expandButtonTopConstraintInCollapse = expandButton.topAnchor.constraint(equalTo: descriptionLabel.lastBaselineAnchor, constant: 12).priority(.required - 1)
         collapseConstraints.append(expandButtonTopConstraintInCollapse)
         
         let expandButtonTopConstraintInExpand = expandButton.topAnchor.constraint(equalTo: expandBox.bottomAnchor, constant: 8).priority(.defaultHigh)
@@ -292,7 +279,7 @@ extension PickServerCell {
         descriptionLabel.setContentHuggingPriority(.required - 2, for: .vertical)
         descriptionLabel.setContentCompressionResistancePriority(.required - 2, for: .vertical)
         
-        expandButton.addTarget(self, action: #selector(expandButtonDidClicked(_:)), for: .touchUpInside)
+        expandButton.addTarget(self, action: #selector(expandButtonDidPressed(_:)), for: .touchUpInside)
     }
     
     private func makeVerticalInfoStackView(arrangedView: UIView...) -> UIStackView {
@@ -305,8 +292,31 @@ extension PickServerCell {
         arrangedView.forEach { stackView.addArrangedSubview($0) }
         return stackView
     }
+
+    override func setSelected(_ selected: Bool, animated: Bool) {
+        super.setSelected(selected, animated: animated)
+        if selected {
+            checkbox.image = UIImage(systemName: "checkmark.circle.fill")
+        } else {
+            checkbox.image = UIImage(systemName: "circle")
+        }
+    }
     
-    private func updateMode() {
+    @objc
+    private func expandButtonDidPressed(_ sender: UIButton) {
+        os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s", ((#file as NSString).lastPathComponent), #line, #function)
+        delegate?.pickServerCell(self, expandButtonPressed: sender)
+    }
+}
+
+extension PickServerCell {
+    
+    enum ExpandMode {
+        case collapse
+        case expand
+    }
+    
+    func updateExpandMode(mode: ExpandMode) {
         switch mode {
         case .collapse:
             expandBox.isHidden = true
@@ -318,73 +328,35 @@ extension PickServerCell {
             expandButton.isSelected = true
             NSLayoutConstraint.activate(expandConstraints)
             NSLayoutConstraint.deactivate(collapseConstraints)
-            
-            updateThumbnail()
         }
     }
     
-    override func setSelected(_ selected: Bool, animated: Bool) {
+//    private func updateThumbnail() {
-        super.setSelected(selected, animated: animated)
+//        guard let serverInfo = server,
-        if selected {
+//              let proxiedThumbnail = serverInfo.proxiedThumbnail,
-            checkbox.image = UIImage(systemName: "checkmark.circle.fill")
+//              let url = URL(string: proxiedThumbnail) else {
-        } else {
+//            thumbnailImageView.isHidden = true
-            checkbox.image = UIImage(systemName: "circle")
+//            thumbnailActivityIdicator.stopAnimating()
-        }
+//            return
-    }
+//        }
+//
+//        thumbnailImageView.isHidden = false
+//        thumbnailActivityIdicator.startAnimating()
+//
+//        let placeholderImage = UIImage.placeholder(color: .systemFill).af.imageRounded(withCornerRadius: 3.0, divideRadiusByImageScale: true)
+//        thumbnailImageView.af.setImage(
+//            withURL: url,
+//            placeholderImage: placeholderImage,
+//            filter: AspectScaledToFillSizeWithRoundedCornersFilter(size: thumbnailImageView.frame.size, radius: 3),
+//            imageTransition: .crossDissolve(0.33),
+//            completion: { [weak self] response in
+//                guard let self = self else { return }
+//                switch response.result {
+//                case .success, .failure:
+//                    self.thumbnailActivityIdicator.stopAnimating()
+//                }
+//            }
+//        )
+//    }
     
-    @objc
-    private func expandButtonDidClicked(_ sender: UIButton) {
-        let newMode: Mode = mode == .collapse ? .expand : .collapse
-        delegate?.pickServerCell(modeChange: server!, newMode: newMode, updates: { [weak self] in
-            self?.mode = newMode
-        })
-    }
-}
-
-// MARK: - Methods to update data
-extension PickServerCell {
-    private func updateServerInfo() {
-        guard let serverInfo = server else { return }
-        domainLabel.text = serverInfo.domain
-        descriptionLabel.text = {
-            guard let html = try? HTML(html: serverInfo.description, encoding: .utf8) else {
-                return serverInfo.description
-            }
-            
-            return html.text ?? serverInfo.description
-        }()
-        langValueLabel.text = serverInfo.language.uppercased()
-        usersValueLabel.text = parseUsersCount(serverInfo.totalUsers)
-        categoryValueLabel.text = serverInfo.category.uppercased()
-    }
-    
-    private func updateThumbnail() {
-        guard let serverInfo = server else { return }
-        
-        thumbnailActivityIdicator.startAnimating()
-        let placeholderImage = UIImage.placeholder(color: .systemFill).af.imageRounded(withCornerRadius: 3.0, divideRadiusByImageScale: true)
-        thumbnailImageView.af.setImage(
-            withURL: URL(string: serverInfo.proxiedThumbnail ?? "")!,
-            placeholderImage: placeholderImage,
-            filter: AspectScaledToFillSizeWithRoundedCornersFilter(size: thumbnailImageView.frame.size, radius: 3),
-            imageTransition: .crossDissolve(0.33),
-            completion: { [weak self] response in
-                guard let self = self else { return }
-                switch response.result {
-                case .success, .failure:
-                    self.thumbnailActivityIdicator.stopAnimating()
-                }
-            }
-        )
-    }
-    
-    private func parseUsersCount(_ usersCount: Int) -> String {
-        switch usersCount {
-        case 0..<1000:
-            return "\(usersCount)"
-        default:
-            let usersCountInThousand = Float(usersCount) / 1000.0
-            return String(format: "%.1fK", usersCountInThousand)
-        }
-    }
 }

Mastodon/Scene/Onboarding/PickServer/TableViewCell/PickServerSearchCell.swift

@@ -8,7 +8,7 @@
 import UIKit
 
 protocol PickServerSearchCellDelegate: class {
-    func pickServerSearchCell(didChange searchText: String?)
+    func pickServerSearchCell(_ cell: PickServerSearchCell, searchTextDidChange searchText: String?)
 }
 
 class PickServerSearchCell: UITableViewCell {
@@ -55,6 +55,12 @@ class PickServerSearchCell: UITableViewCell {
         return textField
     }()
     
+    override func prepareForReuse() {
+        super.prepareForReuse()
+        
+        delegate = nil
+    }
+    
     override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
         super.init(style: style, reuseIdentifier: reuseIdentifier)
         _init()
@@ -97,7 +103,7 @@ extension PickServerSearchCell {
 }
 
 extension PickServerSearchCell {
-    @objc func textFieldDidChange(_ textField: UITextField) {
+    @objc private func textFieldDidChange(_ textField: UITextField) {
-        delegate?.pickServerSearchCell(didChange: textField.text)
+        delegate?.pickServerSearchCell(self, searchTextDidChange: textField.text)
     }
 }

Mastodon/Scene/Onboarding/PickServer/View/PickServerCategoryView.swift

@@ -9,14 +9,14 @@ import UIKit
 import MastodonSDK
 
 class PickServerCategoryView: UIView {
-    var category: MastodonPickServerViewModel.Category? {
+//    var category: MastodonPickServerViewModel.Category? {
-        didSet {
+//        didSet {
-            updateCategory()
+//            updateCategory()
-        }
+//        }
-    }
+//    }
     var selected: Bool = false {
         didSet {
-            updateSelectStatus()
+//            updateSelectStatus()
         }
     }
     
@@ -56,44 +56,56 @@ extension PickServerCategoryView {
     private func configure() {
         addSubview(bgView)
         addSubview(titleLabel)
-        
+
         bgView.backgroundColor = Asset.Colors.lightWhite.color
-        
+
         NSLayoutConstraint.activate([
             bgView.leadingAnchor.constraint(equalTo: self.leadingAnchor),
             bgView.trailingAnchor.constraint(equalTo: self.trailingAnchor),
             bgView.topAnchor.constraint(equalTo: self.topAnchor),
             bgView.bottomAnchor.constraint(equalTo: self.bottomAnchor),
-            
+
             titleLabel.centerXAnchor.constraint(equalTo: self.centerXAnchor),
             titleLabel.centerYAnchor.constraint(equalTo: self.centerYAnchor),
         ])
     }
-    
+
-    private func updateCategory() {
+//    private func updateCategory() {
-        guard let category = category else { return }
+//        guard let category = category else { return }
-        titleLabel.text = category.title
+//        titleLabel.text = category.title
-        switch category {
+//        switch category {
-        case .all:
+//        case .all:
-            titleLabel.font = UIFont.systemFont(ofSize: 17)
+//            titleLabel.font = UIFont.systemFont(ofSize: 17)
-        case .some:
+//        case .some:
-            titleLabel.font = UIFont.systemFont(ofSize: 28)
+//            titleLabel.font = UIFont.systemFont(ofSize: 28)
-        }
+//        }
-    }
+//    }
-    
+//
-    private func updateSelectStatus() {
+//    private func updateSelectStatus() {
-        if selected {
+//        if selected {
-            bgView.backgroundColor = Asset.Colors.lightBrandBlue.color
+//            bgView.backgroundColor = Asset.Colors.lightBrandBlue.color
-            bgView.applyShadow(color: Asset.Colors.lightBrandBlue.color, alpha: 1, x: 0, y: 0, blur: 4.0)
+//            bgView.applyShadow(color: Asset.Colors.lightBrandBlue.color, alpha: 1, x: 0, y: 0, blur: 4.0)
-            if case .all = category {
+//            if case .all = category {
-                titleLabel.textColor = Asset.Colors.lightWhite.color
+//                titleLabel.textColor = Asset.Colors.lightWhite.color
-            }
+//            }
-        } else {
+//        } else {
-            bgView.backgroundColor = Asset.Colors.lightWhite.color
+//            bgView.backgroundColor = Asset.Colors.lightWhite.color
-            bgView.applyShadow(color: Asset.Colors.lightBrandBlue.color, alpha: 0, x: 0, y: 0, blur: 0.0)
+//            bgView.applyShadow(color: Asset.Colors.lightBrandBlue.color, alpha: 0, x: 0, y: 0, blur: 0.0)
-            if case .all = category {
+//            if case .all = category {
-                titleLabel.textColor = Asset.Colors.lightBrandBlue.color
+//                titleLabel.textColor = Asset.Colors.lightBrandBlue.color
-            }
+//            }
+//        }
+//    }
+}
+
+#if DEBUG && canImport(SwiftUI)
+import SwiftUI
+
+struct PickServerCategoryView_Previews: PreviewProvider {
+    static var previews: some View {
+        UIViewPreview {
+            PickServerCategoryView()
         }
     }
 }
+#endif

Mastodon/Scene/Onboarding/PinBasedAuthentication/MastodonPinBasedAuthenticationViewController.swift

@@ -39,8 +39,6 @@ final class MastodonPinBasedAuthenticationViewController: UIViewController, Need
     
 }
     
-
-
 extension MastodonPinBasedAuthenticationViewController {
     
     override func viewDidLoad() {

Mastodon/Service/APIService/APIService+Onboarding.swift

@@ -23,7 +23,7 @@ extension APIService {
         return Mastodon.API.Onboarding.categories(session: session)
     }
     
-    func stubCategories() -> [Mastodon.Entity.Category] {
+    static func stubCategories() -> [Mastodon.Entity.Category] {
         return Mastodon.Entity.Category.Kind.allCases.map { kind in
             return Mastodon.Entity.Category(category: kind.rawValue, serversCount: 0)
         }